I once painted my living room a color called “Warm Linen.” On the swatch, it looked like soft cream with a hint of sunlight. On my walls — all four of them, fully painted — it looked like nicotine stains. I stared at it for two weeks before admitting defeat and buying another gallon.

Swatches lie. Store lighting lies. The only thing that tells the truth is paint on your actual wall, in your actual room, under your actual lighting conditions. Here is how to test properly so you buy one gallon, not two.

Get Samples, Not Swatches

Pick three to five colors you like, then buy sample pots — not the free paper swatches. Most paint stores sell 8-ounce samples for $5-8. It feels like wasting money. It is cheaper than repainting a whole room because the swatch was deceptive.

Paint Big Swatches on Multiple Walls

Paint each sample as a 2-foot by 2-foot square on at least two different walls — one near a window, one on an interior wall. The same color looks completely different in morning light versus evening light, north-facing versus south-facing. Paint directly on the wall, not on poster board. The wall texture and existing color affect how the new color reads.

Label each swatch with the color name using painter’s tape. After two days of walking past them at different times of day, you will know which one works.

Check Undertones Before Committing

Every neutral paint has an undertone: pink, yellow, green, blue, or gray. A “greige” that looks perfectly balanced on the swatch can read aggressively pink against your brown sofa. Hold the swatch next to your flooring, your furniture, your countertops — anything that stays in the room permanently. The undertone will reveal itself by comparison.

My One-Inexpensive-Mistake Rule

If you are torn between two colors, buy the sample of the one you are less sure about. If it works, great — you were wrong and you saved money. If it fails, you were right and the other color was the right call. Either way, you only buy one sample.

I now own zero cans of “Warm Linen” and my walls are a color I actually like.